Error in using argparse to read data from Arduino using python - python-2.7

Question

I am using windows 10 and I am reading ECG data using Arduino micro from pin A1. I used the serial plotter without any problems. The Arduino is connected to COM4
However, I want to read that ECG data using python and plot it there (interface). I came over a useful class called: deque. Link: http://electronut.in/plotting-real-time-data-from-arduino-using-python/
I am calling the function from another python file and I am getting this error:
usage: mac1.py [-h] --port PORT
mac1.py: error: argument --port is required
Code:
import serial
from Arduino import Arduino
import time
import Idr
import matplotlib.pyplot as plt
import matplotlib.animation as animation
if __name__ == '__main__':
Idr.main()
Idr.py function:
import sys, serial, argparse
import numpy as np
from time import sleep
from collections import deque
import matplotlib.pyplot as plt
import matplotlib.animation as animation
# plot class
class AnalogPlot:
# constr
def __init__(self, strPort, maxLen):
# open serial port
self.ser = serial.Serial(strPort, 9600)
self.ax = deque([0.0] * maxLen)
self.ay = deque([0.0] * maxLen)
self.maxLen = maxLen
# add to buffer
def addToBuf(self, buf, val):
if len(buf) < self.maxLen:
buf.append(val)
else:
buf.pop()
buf.appendleft(val)
# add data
def add(self, data):
assert (len(data) == 2)
self.addToBuf(self.ax, data[0])
self.addToBuf(self.ay, data[1])
# update plot
def update(self, frameNum, a1):
try:
line = self.ser.readline()
data = [float(val) for val in line.split()]
# print data
if (len(data) == 2):
self.add(data)
a1.set_data(range(self.maxLen), self.ay)
except KeyboardInterrupt:
print('exiting')
return a1,
# clean up
def close(self):
# close serial
self.ser.flush()
self.ser.close()
# main() function
def main():
# create parser
parser = argparse.ArgumentParser(description="LDR serial")
# add expected arguments
parser.add_argument('--port', dest='port', required=True)
# parse args
args = parser.parse_args()
# strPort = '/dev/tty.usbserial-A7006Yqh'
strPort = args.port
print('reading from serial port %s...' % strPort)
# plot parameters
analogPlot = AnalogPlot(strPort, 100)
print('plotting data...')
# set up animation
fig = plt.figure()
ax = plt.axes(xlim=(0, 100), ylim=(0, 1023))
a1, = ax.plot([], [])
anim = animation.FuncAnimation(fig, analogPlot.update,
fargs=(a1),
interval=50)
# show plot
plt.show()
# clean up
analogPlot.close()
print('exiting.')